The invention pertains to multiple unit peer-to-peer event detection systems. More particularly, the invention pertains to such systems wherein the units locally carry out, alone or in combination, alarm verification, event confirmation or delay processes.
Multi-detector monitoring and alarm systems are used to monitor a region for one or more conditions of interest. Known types of conditions include fire, gas, intrusion and the like.
Known systems often incorporate a common control element which is coupled to a plurality of detectors by some form of a bidirectional communication medium. The medium can be wired, electrical or optical, or wireless, infra-red or RF, for example.
It is recognized that false alarms in such systems are undesirable. One known way of reducing false alarms is by carrying out an alarm verification process at the control element. Where a detector senses an ambient condition, such as fire or smoke, above an alarm threshold, the control element receives this information and waits a predetermined period of time without initiating an alarm condition. A temporal window is then initiated during which additional indications of fire from the same or a different detector will cause an immediate system alarm.
Alternately, some of the known systems use a confirmation process. The control element, upon receipt of an alarm indicating signal from a detector, immediately establishes a confirmation window. The detector must continuously exhibit the alarm condition throughout the confirmation period for the control element to accept the signal as indicating a valid alarm condition.
In yet another application, access control systems incorporate entry and exit time delays to permit normal premises entries and exits without causing alarms. In known systems, a common control element receives signals from transducers, for example, switches, indicative of the opening and/or the closing of doors to or from controlled areas.
In known systems, a common control element generates a premises entry delay upon receipt of an entry signal. The delay is provided to enable a legitimate entrant into the region to reset the access monitoring system thereby forestalling the generation of an unnecessary or false alarm.
Known systems also provide an exit delay. A user signals a common control element as to an imminent exit from the monitored region. The control element initiates an exit delay window during which the individual is permitted to exit from the premises without having the control element initiate an alarm.
In known systems, the common control element receives communications from the system detectors and that element carries out the verification, confirmation, or entry/exit delay timing. It would be useful and promote efficiency in such systems if the respective detectors were able to carry out their own timing processes. In such instances, it would be unnecessary for the respective detectors to communicate with the common control element so that that element could then carry out all of the steps of the respective timing function. System overhead could thus be reduced by providing the various detectors with local control over their respective timing processes.
Known systems incorporate hundreds, sometimes thousands, of detectors. Implementing verification, confirmation or delay processing at the common control element in such systems can create significant system overhead and absorb significant hardware resources and processing time. There, as a result, is a continuing need for monitoring systems which will provide comparable functionality in a more effective fashion so as to reduce overhead and provide improved response.
A multi-unit monitoring system includes a plurality of units coupled to a communication medium. Individual units can carry out verification, confirmation or delay processing.
A unit can incorporate an ambient condition sensor of fire or airborne gas. Where local processing at a unit indicates a possible alarm condition, the unit enters a verification mode and waits a predetermined period of time. A predetermined verification period follows. If the respective unit indicates an alarm condition during the verification period, it will immediately enter an alarm state. It can also, at that time, transmit an alarm indicating message to other units.
If the respective unit does not indicate an alarm condition during the verification period, the predetermined period of time is reset. Optionally, a status indicating message can be transmitted to the other units.
Multiple units can cooperate in the verification process. When one unit enters the verification mode, it can send a status message to other units. If one of the other units, which has received the status message, detects a possible alarm condition, that unit or units can immediately go into an alarm state. Alternately, if the receiving unit is already in a verification mode when it receives the status message, it can terminate that mode and immediately enter an alarm state.
By carrying out the verification process locally, the common control element, if present, need not devote resources to the process. Even if the control element keeps track of status messages from various units, this will still represent less overhead than that required in implementing the verification process for all of the units, which could number in the hundreds or thousands.
In yet another embodiment, electrical units can carry out a confirmation process. Where a sensor associated with the unit exhibits a change of state, a confirmation time interval is locally initiated. A status message indicating entry to a confirmation mode can be sent to other units. A change of state message is not sent unless that change of state persists through the entire confirmation time interval. However, where the change of state has extended through the entire interval, a change of state indicating message will be sent at the end of that interval.
In one embodiment, local confirmation can be incorporated into a fire detector, for example. Entry into a state indicative of a possible alarm triggers the confirmation interval. If the respective fire sensor stays in that state throughout the confirmation interval, an alarm message can be sent from the unit at the end of the interval. If the sensor returns to a quiescent state, the time interval is terminated and no alarm message will be sent. In this embodiment, local confirmation will help suppress nuisance alarms.
In yet another embodiment, one or more units can carry out delay processing. When used to control access, for example, a unit that detects an entry into a region delays initiating an alarm for a predetermined period of time. If during this period, the unit is reset, for example using a key card, manual entry of an access code or the like, no alarm signal will be issued. If not reset an alarm will be issued after the time interval has passed.
In another aspect, an exit delay can be provided locally. An individual about to leave a controlled region can signal this intent to a local access control unit by key card, key pad or the like. In response thereto, an exit delay is locally initiated. An optional status message can be sent by the local unit.
No alarm signal will be generated provided an exit from the region takes place during the exit delay interval. Another status message can be sent at the time the exit is sensed, or, at the end of the delay interval.